Closing Bounties before expiration

There's a posted expiration date for bounties and a countdown for how soon they close. But sponsors appear to be able to award a bounty before the expiration. I've had 2-3 instances where I was a couple hours away from posting a bounty that had days left, and it was awarded prior to me posting or the bounty expiring.

I can't find the rules posted if this is working as designed. I'd suggest changing the behavior that the bounty doesn't close until the expiry. If the sponsor wants it sooner, then they can shorten the date. Or making an option that is communicated that the bounty may be awarded early.

Otherwise, I'm finding bounties a waste of time. While I enjoy competing to win a bounties, I'm loath spending my time and resources working on a model to have the contest close early before I can post.